The present invention relates to an arrangement for transmitting a signal from a transmitter to a rail vehicle located on a segment of a track for position finding and information transmission. The transmitter is connected to a track conductor having crossing points installed in the track segment. The rail vehicle contains a receiver unit which receives the transmitted signal and monitors it for phase jumps occurring during passage through the crossing points of the track conductor for finding the location of the rail vehicle.
An arrangement of this type is described in German Patent Application No. 196 27 343. In this arrangement, a receiver unit is provided in or on a rail vehicle which receives a transmitted signal of a control station, supplied to a track conductor featuring crossing points. A flywheel oscillator is contained in the receiver unit, which generates a comparison signal from the received signal, the comparison signal having the same frequency as the received signal and being phase-synchronized with the received signal. The received signal is compared in the receiver unit with the comparison signal with respect to its phase angle as soon as the received signal has dropped below a lower threshold value and subsequently exceeded an upper threshold value; in such a case it is assumed that the received signal has crossed a zero amplitude point and the rail vehicle has passed through a crossing point of the track conductor. If it is established in this phase comparison between received and comparison signals that a 180xc2x0 phase jump has occurred between the two signals, a crossing point identifier is generated, which is used for self-location of the rail vehicle.
The article xe2x80x9cDer Ortungsrechner fxc3xcr die LZB 80 Fahrgerxc3xa4texe2x80x9d (Position finding computer for LZB 80 locomotivesxe2x80x9d), E. Murr, Signal und Draht 83 (1991), 7/8, pp. 190-193), describes a rail vehicle-side antenna arrangement for vehicle-side detection of track conductor crossing points and thus for finding the location of the rail vehicle. This antenna arrangement has two pairs of antennas each having individual antennas spaced 9.90 meters apart. The passage through a crossing point can be detected from the vehicle with each of the two pairs of antennas by monitoring the output signals of both individual antennas of each pair of antennas for phase jumps.
The rail vehicle-side arrangement of two pairs of antennas is also described in the article xe2x80x9cZugsicherungs-und Zugsteuerungssysteme bei der RGB Dxc3xcsseldorfxe2x80x9d (Train safety and train control systems for the Dxc3xcsseldorf railroad, W. Braun, S. Mura, Signal und Draht 81 (1989), Vol. 7/8, pp. 135-141). In this antenna arrangement one pair of antennas is installed on the first bogie and one of pair of antennas on the last bogie.
Austrian Patent No. 267 602 describes a counter that can be provided for measuring track segments from the vehicle, with which the passage through crossing points is counted.
An object of the present invention is to provide an arrangement with which particularly low-interference position finding is possible.
This object is achieved according to the present invention by the fact that an occupancy sensor is installed at a point of entry of the track segment, which detects the entry of the rail vehicle into the track segment and generates an occupancy signal indicating the occupancy of the track segment, and a switchover device assigned to the transmitter is connected to the occupancy sensor and activates the transmitter so that it transmits an unmodulated signal upon receiving the occupancy signal and transmits a modulated signal after a predefined time period thereafter has elapsed, the predefined time period being of a duration such that it is sufficient for rail vehicle-side location finding.
One advantage of the arrangement according to the present invention is that a particularly low-interference location finding of the rail vehicle is achieved, because when the rail vehicle enters a track segment assigned to the control station, an unmodulated transmitted signal, initiated by the switchover device and supplied to the track conductor, is initially generated by the transmitter. This unmodulated transmitted signal is received by the receiver unit, from which the latter generates a phase-synchronized comparison signal which has a particularly high quality with respect to its synchronization with the received signal, because the transmitted signal is still unmodulated shortly after the rail vehicle has entered the track segment, i.e., before the predefined time period has elapsed, and therefore no synchronization errors caused by signal modulation occur in the comparison signal. Since the comparison signal thus has a particularly high degree of synchronization with the received signal, i.e., it is very accurately matched to the received signal with respect to its phase angle, a particularly accurate detection of the crossing points of the track conductor and thus a particularly accurate finding the location of the rail vehicle are possible.
After the predefined time period has elapsed, which has a duration determined by the time period required for finding the location of the rail vehicle, the finding the location of the rail vehicle is completed and information transmission between the control station and the rail vehicle can be initiated.
The arrangement according to the present invention can be advantageously used in railroad stations where very accurate positioning of the rail vehicle at the platform and thus a highly accurate position finding of the rail vehicle is required. After the rail vehicle comes to a stop in the railroad station area, for example, after a predefined time period to be suitably set has elapsed or after the complete stop of the train has been detected by one or more sensors, information transmission from the control station to the stopped rail vehicle and vice versa can take place.
The arrangement according to the present invention can be manufactured in a particularly simple and therefore inexpensive manner if, for example the occupancy sensor is a rail contact or is formed by a track circuit. The operation of track circuits is described, for example, in European Patent No. 573 131.
The present invention also relates to a method of transmitting a signal to a rail vehicle located on a segment of a track for position finding and information transmission, in which the transmitted signal is supplied to a track conductor installed in the track segment and having crossing points using a transmitter, and the transmitted signal is received using a receiver unit of the rail vehicle and is monitored for phase jumps occurring during passage through the crossing points of the track conductor for finding the location of the rail vehicle.
Such a method is also described in German Patent Application No. 196 27 343.
In order to achieve a particularly error-free position finding of the rail vehicle with such a method, according to the present invention, occupancy of the track segment by the rail vehicle is determined and the transmitter is activated so that it transmits an unmodulated signal for position finding when occupancy has been determined. It transmits a modulated signal for information transmission after a predefined time period thereafter has elapsed, the predefined time period being of a duration such that it is sufficient for rail vehicle-side location finding.
The method according to the present invention can be carried out in a particularly inexpensive and therefore advantageous manner if a track circuit or a rail contact is used for determining occupancy.